1. Field of the Invention
The present invention relates to a tool transfer apparatus including gripping force measuring unit for tool holding unit of a tool magazine included in a machining center or the like, and a machining system including the tool transfer apparatus.
2. Description of the Related Art
A tool transfer apparatus has been known which transfers a tool from a tool stocker disposed outside a machine tool to a tool magazine provided with a plurality of grips for attachment and detachment. With this, the tool can be replaced without limitation of the number of tools that can be held by the tool magazine, and automatic machining can be performed by following a machining program.
However, in the tool magazine of a type which holds tools by the grips as described above, repeated tool attachment and detachment cause abrasion or distortion in a grip component to decrease the tool gripping force, thereby disadvantageously causing a trouble such as a tool drop.
Thus, as disclosed in Japanese Patent No. 3348392, a grip life detecting method to solve this problem has been conventionally known in which the outside of a grip is interposed by a life detecting apparatus using conductive rubber to detect the amount of flexure of the grip, thereby determining a grip life. Although the presence or absence of a tool transfer apparatus is not described in Japanese Patent No. 3348392, by using this grip life detecting apparatus also when a tool transfer apparatus is used, a tool drop can be prevented.
However, it is only the grip formed of an integral member as described in Japanese Patent No. 3348392 that a grip life can be determined for by using this scheme and, disadvantageously, a life cannot be determined for a grip of a type which presses a pin or roller by a spring. Moreover, since only the flexure of the grip can be measured, it is impossible to detect a decrease in gripping force due to, for example, abrasion of a portion in contact with the tool. Furthermore, the grip life detecting apparatus is mounted on a tool magazine as a separate apparatus from an apparatus which attaches and detaches a tool to and from a grip, thereby making the structure of the tool magazine complex.